1. Field of the Invention
The present invention relates to an imaging apparatus equipped with an anti-shake (image shake correction/image stabilizing/shake reduction) system.
2. Description of the Related Art
In recent years, mobile electronic devices which are designed mainly for taking still/moving photographic images, such as digital cameras (still-video cameras) and digital camcorders (motion-video cameras), and other mobile electronic devices which are designed to be capable of taking such photographic images as a subsidiary function, such as mobile phones equipped with a camera and smart devices (smart phones or tablet computers, etc.) equipped with a camera, have become widespread, and there has been a demand to miniaturize the imaging units incorporated in these types of mobile electronic devices. In order to miniaturize an imaging unit, it is known to construct an optical system of an imaging unit out of a bending optical system which reflects (bends) light rays using a reflecting surface of a reflector element such as a prism or a mirror. Using a bending optical system in an imaging unit makes it possible to achieve a reduction in thickness of the imaging unit, especially in the direction of travel of the incident light emanating from an object which is to be photographed.
In addition, there is a demand for imaging units to be equipped with a so-called anti-shake (image shake correction/image stabilizing/shake reduction) system that is designed to reduce image shake on an image plane that is caused by vibrations such as hand shake. The following four different types of imaging units are known in the art as imaging units using a bending optical system which are equipped with an anti-shake system: a first type (disclosed in Japanese Unexamined Patent Publication Nos. 2009-86319 and 2008-268700) in which an image sensor is moved in directions orthogonal to an optical axis to reduce image shake, a second type (disclosed in Japanese Unexamined Patent Publication No. 2010-128384 and Japanese Patent No. 4,789,655) in which a lens disposed behind a reflector element (on the image plane side) that has a reflecting surface is moved in directions orthogonal to an optical axis to reduce image shake, a third type (disclosed in Japanese Unexamined Patent Publication Nos. 2007-228005, 2010-204341, 2006-330439, and Japanese Patent No. 4,717,529) in which the angle of a reflector element (a reflecting surface thereof) and the angle of a lens adjacent to the reflector element are changed to reduce image shake, and a fourth type (disclosed in Japanese Unexamined Patent Publication Nos. 2006-166202 and 2006-259247) in which the entire imaging unit is tilted/inclined to reduce image shake.
An anti-shake system using voice coil motors (VCMs), which generate force (driving force) by application of a current (voltage) across the terminals of the coil positioned inside the magnetic field of a permanent magnet, for driving an optical element (anti-shake optical element) to reduce image shake is known in the art (disclosed in Japanese Unexamined Patent Publication Nos. 2009-86319, 2010-128384, 2007-228005, and Japanese Patent No. 4,789,655). Information on the position of the anti-shake optical element can be obtained with sensors (e.g., Hall sensors) that measure the change in the magnetic field.
The first type of anti-shake system tends to become complicated in structure and tends to increase in cost because a circuit board connected to the image sensor is moved in order to follow movements of the image sensor, which requires electrical components that are provided around the image sensor to also be movable components in addition to the image sensor. In addition, the periphery of the imaging surface of the image sensor is required to be dust tight; however, in small imaging units intended for being incorporated into a mobile phone or a smart device (such as a smartphone, a tablet computer or smart glasses, etc.), it is difficult to secure sufficient space for allowing the image sensor to perform an anti-shake (image shake correction/image-stabilizing/shake reduction) operation while maintaining the dust-tight structure of the image sensor.
The second type of anti-shake system has a structure such that the moving direction of the lens group, disposed behind the reflector element, during an anti-shake operation corresponds to the direction of the thickness of the imaging unit (i.e., the forward/rearward direction of the imaging unit, wherein the direction toward an object to be photographed refers to the forward (front) direction of the imaging unit), and hence, there is a problem with providing enough space to house such an anti-shake structure in a slimmed-down imaging unit. In other words, the slimming-down of the imaging unit is limited if this type of anti-shake system is used. There is a similar problem also in the type of anti-shake system in which an image sensor is moved, instead of a lens group, in the direction of the thickness of the imaging unit.
The third type of anti-shake system requires a large space for allowing the reflector element and the lens group to tilt/incline, and accordingly, the imaging unit is easily enlarged in size. The fourth type of anti-shake system requires a larger space for allowing the entire imaging unit to be tilted/inclined to reduce image shake.
Accordingly, there has been a demand for an anti-shake system that utilizes a different manner for driving an anti-shake optical element from those of the above described types of imaging units and that is advantageous for miniaturization and slimming of the imaging apparatus. A mechanism which supports the anti-shake optical element and a device which gives a driving force to the anti-shake optical element, in particular, have been desired to be simple and compact in size. Additionally, a downsized drive mechanism is also limited in structure and power output of an actuator(s) incorporated therein, thus being required to achieve high-efficient driving.